What Does Pre-Cambrian Mean?

The word Pre-Cambrian is an adjective and you can use the word for something that is pertaining to the earliest era of the history of the earth. The era is believed to be ended almost 570 million years ago. It is this era in which it is believed that the earth-crust was formed and also life first came into existence, though in sea.
     
In the word the prefix 'pre' says that something happened before and the word 'Cambrian' is a word that is used to convey the idea of the first period of the Paleozoic era in which the rocks are believed to be formed. So the word that conveys the idea of a period of time that has happened before Cambrian can be said to be the 'Pre-Cambrian' era.